1. Field of the Invention
This invention relates to a breathing mask having an exhalation valve which is disposed in an opening of the mask wall and includes an outlet for the breathing air which is positioned at the circumference of a thin diaphragm, during inhaling the diaphragm being pulled onto a sealing seat to close the outlet and during exhaling the diaphragm being lifted off the sealing seat to open the outlet.
A breathing mask of this type is known. The prior known mask has an exhalation valve which is inserted into a mask wall opening in the form of a capsule. The capsule includes two annular flanges between which the wall is clamped. In one embodiment, the inner opening of the annular flanges is traversed by reinforcement ribs disposed in star-shaped fashion, on the center of which a circular diaphragm blade is fastened to the outer side of the mask. The diaphragm blade is made of a thin, flexible material and has a diameter which is somewhat greater than the inner diameter of the annular flanges, so that the outer circumference of the diaphragm blade still rests on the outwardly directed surface of the outer flange. At the point where the diaphragm blade rests on the flange, a sealing seat is provided in the form of an annular web having a cross-section which is tapered like a knife in direction towards the diaphragm blade. During exhaling the exhaling air presses from the interior against the diaphragm blade in the areas between the reinforcement ribs and lifts the circumference of the diaphragm blade off from its abutment at the sealing seat, so that the exhaling air is allowed to escape at the outer circumference of the diaphragm blade. During inhaling, on the other hand, the diaphragm blade is pulled into abutment with the sealing as an effect of the vacuum produced
The known exhalation valve, however, is relatively complex due to the plurality of parts which must be produced separately, and assembled. Exhalation valves generally have to open at a relatively low exhaling pressure as their arrangement would be otherwise useless. Consequently, the diaphragm blade of the prior known breathing mask has to be of comparatively thin and light-weight construction to in fact give breathing relief to the person wearing the mask. This means, however, that there is also the risk of malfunction due to diaphragm blades being not exactly flat. For instance, the diaphragm blade freely accessible towards the exterior may be creased by any unintended handling error, so that it can no longer be pulled onto the sealing seat in flat fashion. Furthermore, the diaphragm blade only rests on the comparatively narrow, knifeshaped surface of the sealing seat. Whenever a particle of dust is deposited on this surface, a gap will remain through which unfiltered air is allowed to enter the interior of the breathing mask.
Consequently, the present invention is based on the task of providing a breathing mask having an exhalation valve which opens at a sufficiently low breathing pressure and nevertheless closes safely and reliably during inhaling, and production and assembly of which moreover involves only minor costs.